Micropattern generation with pulsed laser diffraction

ABSTRACT

Methods and devices for preparing microscale polymer relief structures from a thin polymer layer on an absorbing substrate are described. The described methods are ultrafast (about 8 nanoseconds) and allow formation of patterned microstructures having complex morphologies and narrow line widths that are an order of magnitude smaller than the masks used in the methods.

BACKGROUND

There are several known techniques for the generation of controlledmicro-patterns based on self-organization of soft materials. Forexample, controlled dewetting of ultrathin (less than 100 nm) polymerfilms has been extensively studied as a tool for polymer patterning. Thecharacteristic length scales (feature size and wavelength) of dewettingis strongly dependent on the initial thickness of the polymer layer. Thetime scales involved in the dewetting of polymer films are typically onthe order of several minutes, and the structures can be aligned on thescale of the chemically patterned templates .used as substrates fordewetting. A different strategy for polymer patterning involves theformation of surface relief structures in the form of wrinkling andbuckling of polymer films under mechanical stresses generated duringstretching/compression and differential swelling/shrinkage. Thecharacteristic length scales of the wrinkling and buckling scales withlayer thickness and stresses in the layer and substrate. Another widelystudied technique for the patterning of laser-absorbing polymers andother hard materials like metals, glass, and ceramics is laser ablation.Depending on its absorption and interaction with the material, laserirradiation may cause material removal or modify it chemically orphysically. However, a low absorption coefficient of some polymers, suchas polystyrene and polymethylmethacrylate, can make pattern formation bylaser ablation difficult unless modifications are made to enhance theoptical absorption of these polymers.

SUMMARY

This disclosure is not limited to the particular systems, devices andmethods described, as these may vary. The terminology used in thedescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope. While variouscompositions and methods are described in terms of “comprising” variouscomponents or steps (interpreted as meaning “including, but not limitedto”), the compositions and methods can also “consist essentially of”or“consist of”the various components and steps, and such terminologyshould be interpreted as defining essentially closed-member groups.

Embodiments describe methods and devices for preparing microscalepolymer relief structures from a thin polymer layer on an absorbingsubstrate. Localized heating of the substrate by absorption ofdiffracted electromagnetic radiation and subsequent reorganization ofthe polymer layer may allow the polymer to self-organize into patternedperiodic relief structures. Use of a pulsed laser may allow thesemethods to be ultrafast and suitable for continuous fabrication, whileremaining simple, flexible, and direct.

In various embodiments, a method for preparing microscale polymer reliefstructures includes providing a substrate coated with at least onepolymer layer, exposing the substrate and the at least one polymer layerto electromagnetic radiation, producing heat from the energy absorbed bythe substrate, and reorganizing the polymer layer with the produced heatto prepare microscale polymer relief structures.

In various embodiments, a device for preparing periodic microscalepolymer relief structures includes a source of electromagneticradiation, a periodic aperture, and a stage configured to allow asubstrate positioned on the stage to be irradiated by electromagneticradiation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides exemplary microscopy images and plots showing thedependence of characteristic length-scales of the pattern on the polymerlayer thickness in accordance with an embodiment. (a) Mean separation ofridges, (L_(c)) as a function of layer thickness (h). Insets showoptical micrographs of the ridges resulting from polymer films withthicknesses 68 nm, 145 nm and 294 nm, respectively. (b) Ridge width(w_(c)) as a function of layer thickness (h). Insets show opticalmicrographs of the ridges resulting from polymer films with thicknesses86 nm, 135 nm and 280 nm, respectively (Scale bars: 50 μm).

FIG. 2 is a schematic diagram of an exemplary experimental setup, inaccordance with an embodiment.

FIG. 3 is a graph showing simulated 2-dimensional Fresnel diffractionpatterns and corresponding 1-dimensional intensity profiles for Fresnelnumbers, 1 to 6.

FIG. 4 provides exemplary optical images of experimentally generatedpatterns, simulated diffraction patterns, and overlays of the twopatterns. Comparisons for F˜4 (a) and F˜6 (b) (Scale bars: 50 μm).

FIG. 5 shows a simulated diffraction pattern and optical images ofexperimentally generated patterns: (a) Simulated intensity distributioncorresponding to F=8, and patterns formed on polystyrene films having athickness of: (b) 39 nm, (c) 91 nm, and (d) 175 nm (Scale bars: 50 μm).

FIG. 6 provides exemplary optical micrographs of a periodic aperture andexperimentally generated patterns: (a) the square-opening TEM grid usedfor patterning, and (b), (c), (d), (e) and (f) correspond to a patternedpolystyrene layer of thickness 81 nm and different Fresnel number: F˜2,4, 5, 6, and 8, respectively. Insets show the enlarged unit-cell patternformed within each aperture opening (Scale bar: 100 μm).

FIG. 7 provides exemplary optical micrographs of a periodic aperture andexperimentally generated patterns: (a) a 400 mesh square opening TEMgrid used for patterning, (b) patterned polymethylmethacrylate layer ofthickness 98 nm for F˜2, (c) patterned polymethylmethacrylate layer ofthickness 78 nm F<1, and (d) patterned polymethylmethacrylate layer ofthickness 78 nm F˜2(Scale bar: 50 μm).

FIG. 8 provides exemplary optical micrographs of a periodic aperture andexperimentally generated patterns: (a) a hexagonal opening TEM grid usedfor patterning, (b) F˜9, (c) F˜4, and (d) F˜1 (Scale bar: 100 μm).

FIG. 9 provides exemplary optical micrographs of a periodic aperture andexperimentally generated patterns: (a) a rectangular openings of the TEMgrid used as a mask, (b) patterned polystyrene layer of thickness 138 nmwith F˜4, (c) patterned polystyrene layer of thickness 75 nm with F˜1,and (d) patterned polystyrene layer of thickness 75 nm with F˜2 (Scalebar: 50 μm).

DETAILED DESCRIPTION

Methods and devices for preparing microscale polymer relief structuresfrom a thin polymer (less than or equal to about 500 nm) layer on anabsorbing substrate are described herein. hi general, the polymer reliefstructures are formed by heating a substrate irradiating withelectromagnetic radiation. The substrate may absorb the electromagneticradiation which allows reorganization of the polymer layer intoself-organize into relief structures. In some embodiments, line widthsof the relief structures may be tuned by adjusting the thickness of thepolymer layer. In some embodiments, the electromagnetic radiation may bepassed through a periodic aperture which may cause localizedreorganization of the polymer layer allowing relief structures to formperiodic patterns, and in certain embodiments, individual units of theperiodic pattern may be more than an order of magnitude smaller than theopenings of the periodic aperture. The periodic patterns obtained bypassing the electromagnetic energy through a periodic aperture may morestructurally complex than the openings in the periodic aperturesallowing “beyond-the-mask” patterning. In particular embodiments, theelectromagnetic radiation may be provided by a pulsed laser which couldallow these methods to be ultrafast and suitable for continuousfabrication, while remaining simple, flexible, and direct.

Some embodiments include a method for preparing microscale polymerrelief structures including providing a substrate coated with at leastone polymer layer and exposing the substrate and the at least onepolymer layer to electromagnetic radiation. In some embodiments, thesubstrate may absorb energy from at least a portion of theelectromagnetic radiation, and heat may be generated as a result of theabsorbed energy. At least a portion of the at least one polymer layermay be reorganized as a result of the heat generated, and microscalepolymer relief structures may be produced as a result of thereorganization. Exposure of the substrate and the at least one polymerlayer to electromagnetic radiation may be used as a non-ablative processwithout loss of material. In various embodiments, the substrate mayinclude silicon, quartz, glass, indium tin oxide coated glass, atransparent conducting oxide, an absorbing polymer, or combinationsthereof. The polymer layer may, generally, be substantially transparentto the electromagnetic radiation used. For example, in some embodiments,the at least one polymer layer may be polystyrene,polymethylmethacrylate, polyvinyl acetate, polyethylene, polypropylene,and combinations thereof.

In various embodiments, the thickness of each polymer layer may be about10 nm to about 500 micrometers, more specifically, about 10 nm, about 20nm, about 50 nm, about 100 nm, about 500 nm, about 800 nm, about 1micrometer, about 5 micrometers, about 10 micrometers, about 20micrometers, about 50 micrometers, about 75 micrometers, about 100micrometers, about 250 micrometers, about 500 micrometers, and any valueor range of values between any two of these values. In some embodiments,each polymer layer may be coated onto the substrate by any method. Forexample, non-limiting techniques for coating the substrate with apolymer layer may include surface-initiated polymerization, painting,pouring, spraying, dipping, evaporating, spin coating, pressing,contacting, and combinations thereof.

The power, or fluence, of the electromagnetic radiation may vary amongembodiments. For example, in some embodiments, the fluence may be about100 mJ per cm² to about 400 mJ per cm², and in other embodiments, thefluence about 250 mJ cm². Specific examples of fluence include about 100mJ per cm², about 150 mJ per cm², about 200 mJ per cm², about 250 mJ percm², about 300 mJ per cm², about 350 mJ per cm², about 400 mJ per cm²,and any value or range of values between any two of these values. Inparticular embodiments, the power or fluence may be dependent onsubstrate selection, polymer type, polymer thickness, anticipatedmicroscale polymer relief structure, or a combination thereof.

In certain embodiments, exposing the substrate and the at least onepolymer layer to electromagnetic radiation may include irradiating thesubstrate and polymer layer with a laser, and the laser may have afundamental emission wavelength. Non-limiting examples of the types oflasers that can be used in conjunction with the methods described hereininclude gas lasers, chemical lasers, dye lasers, metal-vapor lasers,solid-state lasers, and semiconductor lasers. In particular embodiments,the laser may be a neodymium-doped yttrium aluminum garnet laser. Insome embodiments, the fundamental wavelength of an available laser maynot be suitable and may be converted to a desired wavelength using knownfrequency conversion methods. Non-limiting examples of frequencyconversion methods include passing the laser through at least oneadditional optic such as, for example, non-linear optics, opticalparametric amplifiers, dichroic mirrors, diffraction gratings,collimators, convergent optics, divergent optics, and combinationsthereof In some embodiments, the fundamental wavelength of the laser maybe converted to the second, third, fourth, or fifth harmonic of thefundamental wavelength.

The laser used in some embodiments may be a pulsed laser. In someembodiments, the pulsed laser may have a pulse width of about 1femtosecond to about 1 microsecond, more specifically, 1 femtosecond,about 100 femtoseconds, about 250 femtoseconds, 500 femtoseconds, about1 nanoseconds, about 5 nanoseconds, about 10 nanoseconds, about 15,nanoseconds, about 25 nanoseconds, about 50 nanoseconds, about 75nanoseconds, about 100 nanoseconds, about 250 nanoseconds, about 500nanoseconds, about 1 microsecond, and any value or range of valuesbetween any two of these values. In particular embodiments, the pulsedlaser may have a pulse width of about 8 nanoseconds. In someembodiments, each irradiating step may occur when a single pulse fromthe pulsed laser irradiates the substrate, and in certain embodiments, arelief pattern may be produced with each pulse.

The desired wavelength, or energy, of the electromagnetic radiation mayvary among embodiments and may be dependent on substrate selection,polymer type, polymer thickness, anticipated microscale polymer reliefstructure, periodic aperture, or a combination thereof. In someembodiments, the wavelength may be selected such that the substrateabsorbs at least enough energy to be heated by the electromagneticradiation, and the polymer layer may be substantially transparent toelectromagnetic radiation at this wavelength. Specific examples ofwavelength include about 100 nm, about 150 nm, 200 nm, about 250 nm,about 300 nm, about 350 nm, about 400 nm, about 600 nm, about 1000 nm,about 1,200 nm, about 1,500 nm, and any value or range of values betweenany two of these values. In particular embodiments, the electromagneticradiation may be light having a wavelength of about 355 nm.

In various embodiments, exposing a substrate coated with at least onepolymer layer to electromagnetic radiation may cause heating of thesubstrate and subsequent reorganizing of the polymer layer into polymerrelief structures. In some embodiments, reorganizing the polymer layermay include melting at least a portion of each polymer layer and coolingthe melted portion. In other embodiments, reorganizing the polymer layermay include plastic deformation of at least a portion of the eachpolymer layer.

The morphologies of the polymer relief structures may depend onsubstrate selection, polymer type, polymer thickness, periodic aperture,or a combination thereof. In some embodiments, the microscale polymerrelief structures may resemble a wrinkle-like surface including avariety of dispersed polymer ridges with each ridge having a height,width, and length. As shown in FIG. 1, the space between -100 eachpolymer ridge and the Width -110 of the polymer ridges may increase withthe thickness of the polymer layer.

Various embodiments of methods for preparing microscale polymer reliefstructures may include providing a periodic aperture -200 separated by adistance -210 from the substrate coated with at least one polymer layerand passing electromagnetic radiation through the periodic aperturebefore exposing the substrate coated with at least one polymer layer tothe electromagnetic radiation. In some embodiments, the periodicaperture may . comprise a grid having components selected from squares,-220 rectangles, -230 hexagons, -240 or combinations thereof. Specificexamples of grid components are circles, slits, squares, rectangles,crosses, overlapping circles, overlapping squares, overlappingrectangles, frames, rings, and half circles. In certain embodiments, theperiodic aperture may be a transmission electron microscopy grid.

Passing the electromagnetic radiation through the periodic aperture mayinclude creating a near-field diffraction pattern of electromagneticradiation, and this near-filed diffraction pattern may have intensitymaxima and intensity Minima on the substrate. As shown in FIG. 4, themicroscale polymer relief structures may include a periodic patternhaving features -400 matching the intensity maxima of the near-fielddiffraction pattern -410. The similarities may be observed by overlaying-420 the relief structures with the simulated diffraction pattern. Inthese embodiments, the individual units of the periodic pattern may beabout 22 percent to about 66 percent smaller than openings of theperiodic aperture.

The intensity maxima and minima of the diffraction pattern can bedescribed using a Fresnel Number, F, defined as: F=αΛ2/(λ*l), where α ishalf the aperture width, l is the distance of the aperture from thesubstrate, and λ is the wavelength of the electromagnetic radiation. TheFresnel number can be varied by adjusting the distance of the periodicaperture from the substrate, and in some embodiments, changing theFresnel Number can cause the diffraction pattern, and as such, themicro-relief structures, to change. FIG. 3 shows the effect variousFresnel Numbers have on the complexity and the intensity minima andmaxima. of simulated diffraction patterns using a. square aperture.

Other embodiments include a device for preparing periodic microscalepolymer relief structures. Such devices can include any number ofcomponents including, for example, a source of electromagneticradiation, a periodic aperture arranged to allow electromagneticradiation from the source of electromagnetic radiation to pass throughthe periodic aperture, and a stage configured and arranged to allow asubstrate positioned on the stage to be separated by a distance from theperiodic aperture and irradiated by electromagnetic radiation from thesource after the electromagnetic radiation has passed through theperiodic aperture.

In some embodiments, the source of electromagnetic radiation may becapable of producing light having a wavelength of about 355 nm with afluence of about 100 to 400 mJ per cm², and the source ofelectromagnetic radiation may be a laser; wherein the properties of thelaser, including laser type, pulse length, fluence, and wavelength, maybe selected from those described previously. In further embodiments, thedevice may include one or more additional optical elements selected fromnon-linear optics, optical parametric amplifiers, dichroic mirrors,diffraction gratings, collimators, convergent optics, divergent optics,and combinations thereof.

The periodic aperture and the stage may be arranged to allow creation ofa near-field diffraction pattern of electromagnetic radiation intensitymaxima and minima on a substrate positioned on the stage. In someembodiments, the periodic aperture and the stage may be configured toallow the distance separating the periodic aperture from the substrateto be adjusted.

The periodic aperture of such embodiments may be a grid havingindividual components such as squares, rectangles, hexagons, orcombinations thereof. Specific examples of grid components are circles,slits, squares, rectangles, crosses, overlapping circles, overlappingsquares, overlapping rectangles, frames, rings, and half circles. Infurther embodiments, the periodic aperture may be removable from thedevice. In some embodiments, the periodic aperture may be a transmissionelectron microscopy grid.

In various embodiments, the substrates used in the device may beflexible or rigid. In some embodiments, a substrate supply reel forholding a non-irradiated substrate may be configured and arranged toallow the substrate to be transferred to the stage and to be irradiatedwith electromagnetic energy. In such embodiments, a substrate windingreel for holding irradiated substrate may be configured and arranged tocollect the substrate from the stage after irradiation. In otherembodiments, a substrate conveyor for supporting the substrate may beconfigured and arranged to transport the substrate through at least aportion of the device. Specific examples of conveyers include, but arenot limited to, clamps, spindles, belts, trays, robotic arms, andcombinations thereof. In some embodiments, the substrate conveyer mayprovide support for the substrate during irradiation and, thus, act asthe stage. A separate stage may, therefore, be optional in suchembodiments.

In some embodiments, the substrate may be coated with at least onepolymer layer outside of the device. In other embodiments, a portion ofthe device may be configured to coat the substrate with at least onepolymer layer. In such embodiments, the device may include at least oneadditional component for applying a polymer layer and the component mayapply the polymer by, for example, painting, pouring, spraying, dipping,evaporating, spin coating, pressing, contacting, and combinationsthereof. In some embodiments, the device may include a polymer supplyreel for holding an unstructured polymer film, and the supply reel maybe configured and arranged to allow the polymer film to contact thesubstrate while the substrate is irradiated with electromagnetic energy.In such embodiments, the device may further include a polymer windingreel for holding structured polymer film that is configured and arrangedto collect the polymer film after contacting the substrate.

In some embodiments, the device may include the individual componentsfor preparing periodic microscale polymer relief structures and may beself-contained. In other embodiments, a housing may operably connect thecomponents of the device. For example, a housing may operably connectthe source of electromagnetic radiation, the periodic aperture, thesubstrate, and any additional optional components. In other embodiments,at least one component of the device may be detached from the othercomponents. For example, in particular embodiments, the source ofelectromagnetic radiation may be detached or detachable from a housingoperably connecting the periodic aperture, the substrate, and anyoptional components.

EXAMPLES Example 1 Polymer Layers on Silicon.

Polystyrene (M_(n)=280,000) and polymethylmethacrylate (M_(n)=120,000)were spin coated onto thoroughly cleaned silicon wafer substrates tocreate polymer layers with thicknesses ranging from 30 nm to 400 nmusing 0.5-5 w/v % polymer solutions in HPLC grade toluene.

Example 2 Optimization of Laser Fluence.

The fundamental wavelength (1064 nm) from a neodymium-doped yttriumaluminum garnet nanosecond pulsed laser (Quanta-Ray® Lab, SpectraPhysics, pulse width˜8 ns) was converted to its third harmonic (355 nm),and used to irradiate the polymer layers from Example 1. The fluence wasvaried between 100-400 mJ cm⁻² and tuned to the onset of visible surfacepatterns and to avoiding film rupture, which was˜250 mJ cm⁻²

Example 3

Effect of the Laser Beam on the Polymer Layer without Using an Aperture.

Polymer layers from Example 1 were irradiated with a single laser pulsefrom the laser described in Example 2 set at˜250 mJ cm⁻². Randomlydistributed polymer ridges creating a wrinkle-like surface appeared onthe films of both polystyrene and polymethylmethacrylate. The ridge linewidth (w_(c)) and the mean separation between the ridges (L_(c)) wereboth found to increase linearly with layer thickness. Relatively thickfilms (100 nm-400 nm) showed well developed, smooth, but sparsepatterns. As the thickness decreased, the patterns became denser andmore fragmented.

Example 4 Correlation of Polymer Relief Patterns and SimulatedDiffraction Patterns.

Patterned polymer relief structures were formed using 81 nm polystyrenelayers on silicon from Example 1, a single laser pulse from the laserdescribed in Example 2, an aperture with a grid of 110 μm squareopenings, and Fresnel Numbers (F) of 4 and 6. Optical images of thepatterned polymer relief structures were overlaid with a simulatedintensity pattern corresponding to the same F (FIG. 4). The polymerrelief structures were found to form where the laser simulated intensitywas higher.

Example 5 Effect of Polymer Thickness on Pattern Formation.

Patterned polymer relief structures were formed using 39 nm, 91 nm, and175 nm polystyrene layers on silicon from Example 1, a single laserpulse from the laser described in Example 2, an aperture with a grid of110 μm square openings, and a Fresnel Numbers (F) of 8. As shown in FIG.5, the 39 nm thick polymer layer made a pattern that was comparable tothe simulated diffraction pattern, with the polymer patterncorresponding to each intensity maxima. Finer details started todisappear for the 91 nm thick layer, and only the gross pattern with adistorted interior was seen. Only the outer square pattern was observedfor the 175 nm thick layer.

Example 6 Effect of F on Pattern Formation.

Patterned polymer relief structures were formed using 81 nm polystyrenelayers on silicon from Example 1, a single laser pulse from the laserdescribed in Example 2, an aperture with a grid of 110 μm squareopenings, and Fresnel Numbers (F)of 2, 4, 5, 6 and 8. FIG. 6 shows thatfor relatively small values of F (F≦4), the diffraction patterns ofneighboring cells interfered to form a more continuous pattern, whichresulted in less distinct boundaries of unit cells. Finer featuresappeared within a unit-cell pattern when F was large (F≧5).

Example 7 Effect of Smaller Aperture on Pattern Formation.

Patterned polymer relief structures were formed using 78 nm and 98 nmpolymethylmethacrylate layers on silicon from Example 1, a single laserpulse from the laser described in Example 2, an aperture with a grid of36 μm square openings, and Fresnel Numbers (F)of 1 and 2. FIG. 7 showsthat the patterns formed using the 98 nm thick layer formed a ring-likepattern in each aperture opening; while the patterns formed using the 78nm thick layer formed more complex star-shaped patterns.

Example 8 Effect of Hexagonal Grid Aperture on Pattern Formation.

Patterned polymer relief structures were formed using 98 nmpolymethylmethacrylate layers on silicon from Example 1, a single laserpulse from the laser described in Example 2, an aperture with a grid of55 μm hexagonal openings, and Fresnel Numbers (F)of 9, 4, and 1. FIG. 8,shows the resulting six-fold symmetric star-shaped patterns. The averagesize of the patterned unit-cells was about 36 μm, about 35% smaller thanthe mask opening, with a line width of about 2 μm.

Example 9 Effect of Rectangular Arid Aperture on Pattern Formation.

Patterned polymer relief structures were formed using 138 nm and 75 nmpolystyrene layers on silicon from Example 1, a single laser pulse fromthe laser described in Example 2, an aperture with a grid of 282 μm by36 μm rectangular openings, and Fresnel Numbers (F)of 4, 2, and 1. FIG.8, shows that arrays of polymers channels can be fabricated withcontrolled dimensions.

In the present disclosure, reference is made to the accompanyingfigures, which form a part hereof. The illustrative embodimentsdescribed in the detailed description, figure, and claims are not meantto be limiting. Other embodiments may be used, and other changes may bemade, without departing from the spirit or scope of the subject matterpresented herein. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe figure, may be arranged, substituted, combined, separated, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated herein.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various aspects. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent methods andapparatuses within the scope of the disclosure, in addition to thoseenumerated herein, will be apparent to those skilled in the art from theforegoing descriptions. Such modifications and variations are intendedto fall within the scope of the appended claims. The present disclosureis to be limited only by the terms of the appended claims, along withthe full scope of equivalents to which such claims are entitled. It isto be understood that this disclosure is not limited to particularmethods, reagents, compounds, compositions or biological systems, whichcan, of course, vary. It is also to be understood that the terminologyused herein is for the purpose of describing particular embodimentsonly, and is not intended to be limiting.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to embodiments containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should be interpreted to mean “at least one”or “one or more”); the same holds true for the use of definite articlesused to introduce claim recitations. In addition, even if a specificnumber of an introduced claim recitation is explicitly recited, thoseskilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number (e.g., the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations). Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,etc.” is used, in general such a construction is intended in the senseone having skill in the art would understand the convention (e.g., “asystem having at least one of A, B, and C” would include but not belimited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, etc.). It will be further understood by those within the artthat virtually any disjunctive word and/or phrase presenting two or morealternative terms, whether in the description, claims, or figure, shouldbe understood to contemplate the possibilities of including one of theterms, either of the terms, or both terms. For example, the phrase “A orB” will be understood to include the possibilities of “A” or “B” or “Aand B.”

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, such as in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” and the like include the number recited andrefer to ranges which can be subsequently broken down into subranges asdiscussed above. Finally, as will be understood by one skilled in theart, a range includes each individual member. Thus, for example, a grouphaving 1-3 substituents refers to groups having 1, 2, or 3 substituents.Similarly, a group having 1-5 substituents refers to groups having 1, 2,3, 4, or 5 substituents, and so forth.

1. A method for preparing microscale polymer relief structures, themethod comprising: providing a substrate coated with at least onepolymer layer; exposing the substrate and the at least one polymer layerto electromagnetic radiation, the electromagnetic radiation havingenergy that is absorbed by the substrate; producing heat from the energyabsorbed by the substrate; reorganizing the polymer layer with theproduced heat to prepare microscale polymer relief structures; providinga periodic aperture separated by a distance from the substrate coatedwith at least one polymer layer; and passing electromagnetic radiationthrough the periodic aperture before exposing the substrate coated withat least one polymer layer to the electromagnetic radiation, whereby anear-field diffraction pattern of electromagnetic radiation intensitymaxima and minima is created on the substrate coated with at least onepolymer layer.
 2. The method of claim 1, wherein reorganizing thepolymer layer includes: melting at least a portion of the at least onepolymer layer; and cooling the melted portion of the at least onepolymer layer.
 3. The method of claim 1, wherein reorganizing thepolymer layer includes plastic deformation of at least a portion of theat least one polymer layer.
 4. The method of claim 1, wherein the atleast one polymer layer is substantially transparent to theelectromagnetic radiation.
 5. (canceled)
 6. The method of claim 1,wherein the at least one polymer layer comprises a polymer selected fromthe group consisting of polystyrene, polymethylmethacrylate, polyvinylacetate, and combinations thereof.
 7. The method of claim 1, wherein thesubstrate comprises silicon, quartz, glass, indium tin oxide coatedglass, a transparent conducting oxide, or combinations thereof.
 8. Themethod of claim 1, wherein the thickness of the at least one polymerlayer is about 10 nm to about 500 micrometers.
 9. The method of claim 1,wherein exposing the substrate to electromagnetic radiation comprisesirradiating the substrate and the at least one polymer layer with alaser having a fundamental emission wavelength.
 10. The method of claim9, wherein the laser is a pulsed laser.
 11. The method of claim 9,further comprising converting the fundamental wavelength of the laser toa second, third, fourth, or fifth harmonic.
 12. The method of claim 1,wherein the electromagnetic radiation comprises light at about 355 nm.13. The method of claim 1, wherein the electromagnetic radiation has afluence of about 100 mJ per cm² to 400 mJ per cm².
 14. (canceled) 15.The method of claim 1, further comprising adjusting the distanceseparating the periodic aperture from the substrate coated with at leastone polymer layer.
 16. The method of claim 1, wherein the periodicaperture comprises a grid having components selected from squares,rectangles, hexagons, or combinations thereof.
 17. A device forpreparing periodic microscale polymer relief structures, the devicecomprising: a source of electromagnetic radiation; a periodic aperturearranged to allow electromagnetic radiation from the source ofelectromagnetic radiation to pass through the periodic aperture; and astage configured and arranged to allow a substrate positioned on thestage to be separated by a distance from the periodic aperture andirradiated by electromagnetic radiation from the source after theelectromagnetic radiation has passed through the periodic aperture,whereby a near-field diffraction pattern of electromagnetic radiationintensity maxima and minima is created on the substrate.
 18. The deviceof claim 17, wherein the source of electromagnetic radiation is a laser.19. The device of claim 17, wherein the source of the electromagneticradiation is a pulsed laser.
 20. The device of claim 17, furthercomprising at least one additional optic selected from non-linearoptics, optical parametric amplifiers, dichroic minors, diffractiongratings, collimators, convergent optics, divergent optics, andcombinations thereof.
 21. The device of claim 17, wherein the source ofelectromagnetic radiation is capable of producing light having awavelength of about 355 nm.
 22. The device of claim 17, wherein thesource of electromagnetic radiation is capable of producingelectromagnetic radiation having a fluence of about 100 to 400 mJ percm².
 23. The device of claim 17, wherein the periodic aperture and thestage are configured to allow the distance separating the periodicaperture from the substrate to be adjusted.
 24. The device of claim 17,wherein the periodic aperture comprises a grid having componentsselected from squares, rectangles, hexagons, or combinations thereof.25. The device of claim 17, further comprising at least one additionalcomponent for applying a polymer layer to the substrate by a methodselected from painting, pouring, spraying, dipping, evaporating, spincoating, pressing, contacting, and combinations thereof.
 26. The deviceof claim 17, further comprising: a polymer supply reel for holding anunstructured polymer film, the polymer supply reel being configured andarranged to allow the polymer film to contact the substrate while thesubstrate is irradiated with electromagnetic energy; and a polymerwinding reel for holding structured polymer film, the polymer windingreel being configured and arranged to collect the polymer film aftercontacting the substrate.
 27. The device of claim 17, furthercomprising: a substrate supply reel for holding a non-irradiatedsubstrate, the substrate supply reel being configured and arranged toallow the substrate to be irradiated with electromagnetic energy; and asubstrate winding reel for holding irradiated substrate, the substratewinding reel being configured and arranged to collect the substrateafter irradiation.
 28. The device of claim 17, further comprising asubstrate conveyor for supporting the substrate, the substrate conveyorbeing configured and arranged to transport the substrate through atleast a portion of the device.